text: /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
  /*
   * lib/crypto/krb/prf/dk_prf.c
   *
   * Copyright (C) 2004 by the Massachusetts Institute of Technology.
   * All rights reserved.
   *
   * Export of this software from the United States of America may
   *   require a specific license from the United States Government.
   *   It is the responsibility of any person or organization contemplating
   *   export to obtain such a license before exporting.
   *
   * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
   * distribute this software and its documentation for any purpose and
   * without fee is hereby granted, provided that the above copyright
   * notice appear in all copies and that both that copyright notice and
   * this permission notice appear in supporting documentation, and that
   * the name of M.I.T. not be used in advertising or publicity pertaining
   * to distribution of the software without specific, written prior
   * permission.  Furthermore if you modify this software you must label
   * your software as modified software and not distribute it in such a
   * fashion that it might be confused with the original M.I.T. software.
   * M.I.T. makes no representations about the suitability of
   * this software for any purpose.  It is provided "as is" without express
   * or implied warranty.
   *
   *
   *
   * This file contains an implementation of the RFC 3961 PRF for
   *simplified profile enctypes.
   */
  
  #include "prf_int.h"
  #include <dk.h>
  
  krb5_error_code
  krb5int_dk_prf(const struct krb5_keytypes *ktp, krb5_key key,
                 const krb5_data *in, krb5_data *out)
  {
      const struct krb5_enc_provider *enc = ktp->enc;
      const struct krb5_hash_provider *hash = ktp->hash;
      krb5_crypto_iov iov;
      krb5_data cksum = empty_data(), prfconst = make_data("prf", 3);
      krb5_key kp = NULL;
      krb5_error_code ret;
  
      /* Hash the input data into an allocated buffer. */
      ret = alloc_data(&cksum, hash->hashsize);
      if (ret != 0)
          goto cleanup;
      iov.flags = KRB5_CRYPTO_TYPE_DATA;
      iov.data = *in;
      ret = hash->hash(&iov, 1, &cksum);
      if (ret != 0)
          goto cleanup;
  
      /* Derive a key using the PRF constant. */
      ret = krb5int_derive_key(ktp->enc, key, &kp, &prfconst, DERIVE_RFC3961);
      if (ret != 0)
          goto cleanup;
  
      /* Truncate the hash to the closest multiple of the block size. */
      iov.data.data = cksum.data;
      iov.data.length = (hash->hashsize / enc->block_size) * enc->block_size;
  
      /* Encrypt the truncated hash in the derived key to get the output. */
      ret = ktp->enc->encrypt(kp, NULL, &iov, 1);
      if (ret != 0)
          goto cleanup;
      memcpy(out->data, iov.data.data, out->length);
  
  cleanup:
      zapfree(cksum.data, hash->hashsize);
      krb5_k_free_key(NULL, kp);
      return ret;
  }
  